package com.hmdp.utils;


import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import javax.annotation.Resource;
import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

@Slf4j
@Component
public class CacheClient {
    @Resource
    private StringRedisTemplate stringRedisTemplate;

    public void set(String key, Object value, Long time, TimeUnit unit){
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value),time,unit);
    }

    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit){
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        //写入redisdata
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }

    public <R,ID> R queryWithPassThrough(String keyPrefix,ID id,Class<R> type, Function<ID,R> dbFallBack,Long time,TimeUnit unit){//传入前缀，id和类型
        String key = keyPrefix+id;
        //从redis查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //判断是否存在
        if(StrUtil.isNotBlank(json)){
            //存在，直接返回
            return JSONUtil.toBean(json,type);
        }
        if(json!=null){
            return null;
        }//redis有值又不是正常值，只能是""空值
        //不存在，根据id查询数据库
        R r = dbFallBack.apply(id);//由调用者把数据库的调用逻辑返回
        //不存在，返回错误
        if(r==null){
            //将空值写入redis
            stringRedisTemplate.opsForValue().set(key,"",RedisConstants.CACHE_NULL_TTL, TimeUnit.MINUTES);
            return null;
        }

        //存在，写入redis
        this.set(key,r,time,unit);

        //返回
        return r;
    }
    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);


    public <R,ID> R queryWithLogicalExpire(String keyPrefix,ID id,Class<R> type,Function<ID,R> dbFallBack,Long time,TimeUnit unit){

        String key = keyPrefix+id;
        //从redis查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //判断是否存在
        if(StrUtil.isBlank(json)){
            //不存在，直接返回
            return null;
        }
        //命中，需要判断过期时间，反序列化
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        JSONObject data = (JSONObject)redisData.getData();//类型强转,因为存储的是object类型的数据
        R r = JSONUtil.toBean(data, type);
        LocalDateTime expireTime = redisData.getExpireTime();

        //判断是否过期
        if(expireTime.isAfter(LocalDateTime.now())){
            return r;//返回未过期数据
        }
        //已过期，需要缓存重建
        //获取互斥锁
        String lockKey = RedisConstants.LOCK_SHOP_KEY+id;
        boolean isLock = tryLock(lockKey);

        //是否获取锁成功
        if(isLock){
            //成功，开启独立线程，实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(()->{
                //重建缓存
                try {
                    R r1 = dbFallBack.apply(id);
                    this.setWithLogicalExpire(key,r1,time, unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                }
                unlock(lockKey);
            });


        }
        //失败，返回过期信息
        return r;
    }

    //获取锁
    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key,"1",10,TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }


    //释放锁
    private void unlock(String key){
        stringRedisTemplate.delete(key);
    }


}
